AG314

DATASHEET SEARCH SITE | WWW.ALLDATASHEET.COM

Document overview

• Manufacturer or author: Provided By ALLDATASHEET.COM(FREE DATASHEET DOWNLOAD SITE)
• PDF pages: 70

Technical content

Visit www.macomtech.com for additional data sheets and product information. M/A-COM Technology Solutions Inc. and its affiliates reserve the right to make changes to the product(s) or information contained herein without notice. Principles, Applications and Selection of Receiving Diodes Rev. V1 AG314 ADVANCED: Data Sheets contain information regarding a product M/A-COM Technology Solutions is considering for development. Performance is based on target specifications, simulated results, and/or prototype measurements. Commitment to develop is not guaranteed. PRELIMINARY: Data Sheets contain information regarding a product M/A-COM Technology Solutions has under development. Performance is based on engineering tests. Specifications are typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available. Commitment to produce in volume is not guaranteed. INTRODUCTION Many microwave and RF systems require the frequency of a signal to be translated to a higher or lower frequency. Also, there are applications for the generation of a relatively low frequency volt- age or current that is proportional to the amplitude of a higher frequency signal. The properties of a Schottky diode can be exploited to perform these tasks. This application note is a survey of the physical and electrical characteristics of Schottky mixer and detector diodes. It reviews the semiconductor and electrical properties of these diodes and illustrates how they are used in a number of receiving circuits. It also presents a number of tables and criteria to select an appropriate Schottky diode depending on the requirement of the mixer or receiving system. This application note is divided into eight sections: This application note has been the standard Schottky diode reference since it was written in the mid-1980’s. Since then, the fundamental principles of mixer technology and Schottky junction physics have not changed, but many of the implementations of these technologies have evolved and improved. This note has been extensively revised to reflect these advances in diode and circuit design. I. A discussion of the fundamentals of Schottky di odes including the physics of Schottky junctions and their characteristics such as resistance, capacitance and barrier heights. These properties ultimately determine the performance of all mixer and detector diodes. II. A discussion of the principles of variable resist ance mixer diodes and the diodes' RF properties such as noise figure, conversion loss and impedance. III. A discussion of the principles of detector diodes and their RF properties such as sensitivity and video resistance. IV. A comparison of the differences in mixers and detectors when used in receivers. V. A discussion of common mixer, modulator and multiplier circuits which use Schottky diodes. Some of the advantages and disadvantages of different circuits are discussed. VI. A glossary containing definitions of the majo r terms used in discussing mixer and detector cir- cuits and mixer and detector diodes. VII. Tables and graphs to aid in the selection of an appropriate mixer circuit or diode for a circuit based on the system's receiver requirements. VIII. A Selection Guide to help select the most appropriate microwave diode.

Visit www.macomtech.com for additional data sheets and product information. M/A-COM Technology Solutions Inc. and its affiliates reserve the right to make changes to the product(s) or information contained herein without notice. Principles, Applications and Selection of Receiving Diodes Rev. V1 AG314 ADVANCED: Data Sheets contain information regarding a product M/A-COM Technology Solutions is considering for development. Performance is based on target specifications, simulated results, and/or prototype measurements. Commitment to develop is not guaranteed. PRELIMINARY: Data Sheets contain information regarding a product M/A-COM Technology Solutions has under development. Performance is based on engineering tests. Specifications are typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available. Commitment to produce in volume is not guaranteed. TABLE OF CONTENTS A. CURRENT VS VOLTAGE RELATION B. SCHOTTKY DIODE EQUIVALENT CIRCUIT C. TOTAL CAPACITANCE OF A SCHOTTKY DIODE D. SERIES RESISTANCE E. FIGURE OF MERIT A. EQUIVALENT CIRCUIT OF A MIXER DIODE B. BASIC MIXER DIODE RF PARAMETERS C. NOISE IN MIXER DIODES D. OVERALL RECEIVER'S NOISE FIGURE E. MIXER DIODE RF IMPEDANCE F. MIXER DIODE IF IMPEDANCE A. BASIC DETECTOR DIODE CHARACTERISTICS B. THE VIDEO DETECTOR C. DETECTOR DIODE ELECTRICAL CHARACTERISTICS D. NOMINAL DETECTABLE SIGNAL (NDS) E. TANGENTIAL SIGNAL SENSITIVITY (TSS) F. FIGURE OF MERIT (FM) G. VIDEO BANDWIDTH A. CHOICE OF MIXERS VS. DETECTORS A. SINGLE-ENDED MIXERS. B. SINGLE BALANCED MIXERS C. DOUBLE BALANCED MIXERS D. DOUBLE-DOUBLE BALANCED MIXERS E. IMAGE REJECT MIXERS F. SUBHARMONIC MIXERS G. IMAGE RECOVERY MIXERS H. PHASE DETECTORS I. OTHER RING QUAD APPLICATIONS J. BRIDGE QUAD APPLICATIONS K. FREQUENCY MULTIPLIERS L. QUADRATURE PHASE MODULATORS M. FREQUENCY DETERMINATION--A QUADRATURE IF MIXER N. SINGLE SIDEBAND MODULATORS

Visit www.macomtech.com for additional data sheets and product information. M/A-COM Technology Solutions Inc. and its affiliates reserve the right to make changes to the product(s) or information contained herein without notice. Principles, Applications and Selection of Receiving Diodes Rev. V1 AG314 ADVANCED: Data Sheets contain information regarding a product M/A-COM Technology Solutions is considering for development. Performance is based on target specifications, simulated results, and/or prototype measurements. Commitment to develop is not guaranteed. PRELIMINARY: Data Sheets contain information regarding a product M/A-COM Technology Solutions has under development. Performance is based on engineering tests. Specifications are typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available. Commitment to produce in volume is not guaranteed. TABLE OF CONTENTS VI. DEFINITION OF TERMS USED WITH MIXERS, DETECTORS AND RECEIVING A. FREQUENCY TERMS B. TYPES OF MIXERS BY FREQUENCY OUTPUT C. MIXER DIODE TERMS (CHARACTERISTICS) D. DETECTOR DIODE CHARACTERISTICS E. RECEIVER SYSTEM CHARACTERISTICS VII. TABLES TO AID IN THE SELECTION OF AN APPROPRIATE MIXER OR DIODE FOR CIRCUIT BASED ON THE SYSTEM’S RECEIVER REQUIREMENTS…………..….PG68 VIII. A SELECTION GUIDE TO HELP SELECT THE MOST APPROPRIATE MICROWAVE

Visit www.macomtech.com for additional data sheets and product information. M/A-COM Technology Solutions Inc. and its affiliates reserve the right to make changes to the product(s) or information contained herein without notice. Principles, Applications and Selection of Receiving Diodes Rev. V1 AG314 ADVANCED: Data Sheets contain information regarding a product M/A-COM Technology Solutions is considering for development. Performance is based on target specifications, simulated results, and/or prototype measurements. Commitment to develop is not guaranteed. PRELIMINARY: Data Sheets contain information regarding a product M/A-COM Technology Solutions has under development. Performance is based on engineering tests. Specifications are typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available. Commitment to produce in volume is not guaranteed. I. Schottky Diode Fundamentals A Schottky barrier diode uses a rectifying meta l-semiconductor junction formed by plating, evaporating or sputtering one of a variety of metals onto n-type or p-type semiconductor mate- rial. Generally, n-type silicon and n-type GaAs are used in commercially available Schottky di- odes. The properties of a forward bi ased Schottky barrier diode are determined by majority carrier phenomena. A pn junction diode's properties are determined by minority carriers. Schottky di- odes are majority carrier devices that can be swit ched rapidly from forward to reverse bias with- out minority carrier storage effects. Because of this characteristic they make superior micro- wave mixer and detector diodes. The normal current/voltage (I/V) curve of a Schottky barrier diode resembles that of a pn junc- tion diode with the following exceptions: 1. The reverse breakdown voltage of a Schottky barrier diode is lower and the reverse leakage current higher than those of a pn junction diode made using the same resistivity semicon- ductor material. 2. The forward voltage at a specific forward cu rrent is also lower for a Schottky barrier diode than for a pn junction diode. For example, at 2 mA forward bias current a low barrier silicon Schottky diode will have a forward voltage of ~0.3 volts while a silicon pn junction diode will have a voltage of ~0.7 volts. In order to understand the major electrical proper ties of a Schottky barrier diode, the physics of the barrier and the current across the barrier must be understood. Figure 1 shows the electron energy levels in a me tal as a function of distance from the surface of an isolated metal and on an isolated neutral n-type semiconductor with a net negative surface charge, which explains the curvature of the conduction and valence band energy plots. In Figure 1a, e ψ M is the vacuum work function or the po tential required to remove an electron from the Fermi level, W F, to a position outside of the metal. Typical values of e ψM are a few volts. e ψM is a constant value for a given, atomical ly pure metal, but varies with surface con- tamination. In Figure 1b, W V and WC are the energy levels of the semiconductor's valence and conduction bands, respectively. As in the metal, W F is the Fermi level of the semiconductor and is a func- tion of its doping. Note that the Fermi level of the semiconductor is not equal to the Fermi level of the metal. The energies e χ and e ψ S are the energies required to remove an electron from the conduction band and Fermi level respectively to a free position outside the semiconductor.

Visit www.macomtech.com for additional data sheets and product information. M/A-COM Technology Solutions Inc. and its affiliates reserve the right to make changes to the product(s) or information contained herein without notice. Principles, Applications and Selection of Receiving Diodes Rev. V1 AG314 ADVANCED: Data Sheets contain information regarding a product M/A-COM Technology Solutions is considering for development. Performance is based on target specifications, simulated results, and/or prototype measurements. Commitment to develop is not guaranteed. PRELIMINARY: Data Sheets contain information regarding a product M/A-COM Technology Solutions has under development. Performance is based on engineering tests. Specifications are typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available. Commitment to produce in volume is not guaranteed. A. CURRENT VS VOLTAGE RELATION The current/voltage (I/V) relationship for a Schottky barrier diode is given by the following equation known as the Richardson equation. (1) Saturation Current, where: The barrier height of a Schottky diode can be determined experimentally by fitting the forward I/ V characteristic to the Richardson equation. Notice that f B, the potential barrier for electrons in the metal moving towards the semiconductor, influences the forward current. The barrier height is important because it determ ines the local oscillator power necessary to bias the diode into its non-linear region. See Figure 48 for this relationship. In many high fre- quency receiver systems the available local osci llator power is limited so low barrier Schottky diodes must be used. Schottky diodes have been fabricated with several metals and alloys us- ing p- and n-type silicon and n-type gallium arsenide, with barriers ranging from 0.27 eV to 0.90 eV. (See Table I for barrier heights of common metals, compounds and metal mixtures used for silicon & GaAs Schottky diodes). II S e qV nkT 1 I s .AA*T e qB kT= A = junction area A* = modified Richardson constant (value varies by material and dopant) = 110 A/(°K2-cm2) for n-type Si T = absolute temperature in K q = electronic charge = 1.6 * 10 -19 C fB = barrier height in volts k = Boltzman’s constant = 1.37 * 10 -23 J/K n = ideality factor (forward slope factor, determined by metal-semiconductor interface

Visit www.macomtech.com for additional data sheets and product information. changes to the product(s) or information contained herein without notice. and/or prototype measurements. Commitment to develop is not guaranteed. typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available. Commitment to produce in volume is not guaranteed. Table 1. Experimental Values of the More Common Metal Semi- Figure 3. Ideal Schottky Diode I/V Characteristic

Visit www.macomtech.com for additional data sheets and product information. M/A-COM Technology Solutions Inc. and its affiliates reserve the right to make changes to the product(s) or information contained herein without notice. Principles, Applications and Selection of Receiving Diodes Rev. V1 AG314 ADVANCED: Data Sheets contain information regarding a product M/A-COM Technology Solutions is considering for development. Performance is based on target specifications, simulated results, and/or prototype measurements. Commitment to develop is not guaranteed. PRELIMINARY: Data Sheets contain information regarding a product M/A-COM Technology Solutions has under development. Performance is based on engineering tests. Specifications are typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available. Commitment to produce in volume is not guaranteed. Market forces require continually improved, higher frequency electrical performance from semi- conductors with lower prices. These conditions require that diodes be packaged in plastic pack- ages, such as the SOT-23, SOT-323, SOD-323, et c., using automated assembly techniques. However, the implications of these requirements are in mutual opposition. Better performance at higher frequencies requires lower junction capacitance, which is achieved by reducing the area of the metal-semiconductor junction. The optical recognition systems used with automated wire bonding assembly equipment have minimum feature sizes smaller than which they cannot recognize properly. This minimum feature size is much larger than the metal-semiconductor junction area that is required for an RF or microwave Schottky diode. At first glance this problem appears easy to solve by simply increasing the diameter of the metal that is deposited on top of the passivation layers, as shown in Figure 5a, to produce a feature large enough to be optically detected and recognized. This approach can substantially increase the diode’s overlay capacitance (C 0) to the point that the total diode capacitance becomes too large for high frequency operation. Since the minimum top metal size is determined by the capability of the optical recognition sys- tem used, the only alternatives that the diode designer has is to either make the dielectric layers of the overlay capacitance (the passivation layers) thicker or to use materials with lower relative dielectric constant. Recent advances in material science have produced many polymers, one of which, benzo- cyclobutene (BCB) is particularly well suited for use with microwave semiconductors. Its low relative dielectric constant (ε r = 2.7) and dissipation factor along with its superior mechanical strength make BCB a good material to use as a third, topmost layer of dielectric in small Backside Metal Contact Ohmic Contact Substrate Epitaxial Layer Thermal Oxide (SiO2) Nitride (Si3N4) RC J RS RS2 Top Contact Metal BCB CO Figure 5b. Schottky Diode Die with BCB and Equivalent Circuit

Visit www.macomtech.com for additional data sheets and product information. changes to the product(s) or information contained herein without notice. and/or prototype measurements. Commitment to develop is not guaranteed. typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available. Commitment to produce in volume is not guaranteed. with automated assembly. Such a die is shown in Figure 5b. 6 shows an equivalent circuit for a beam lead Schottky device. using SURMOUNT or beam lead diodes. Figure 6. Equivalent Circuit for a MA40415 Beam Lead Device

Visit www.macomtech.com for additional data sheets and product information. M/A-COM Technology Solutions Inc. and its affiliates reserve the right to make changes to the product(s) or information contained herein without notice. Principles, Applications and Selection of Receiving Diodes Rev. V1 AG314 ADVANCED: Data Sheets contain information regarding a product M/A-COM Technology Solutions is considering for development. Performance is based on target specifications, simulated results, and/or prototype measurements. Commitment to develop is not guaranteed. PRELIMINARY: Data Sheets contain information regarding a product M/A-COM Technology Solutions has under development. Performance is based on engineering tests. Specifications are typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available. Commitment to produce in volume is not guaranteed. 1. Junction Capacitance The junction capacitance of a Schottky barrier diode is given by: (3) C j()V ..q  S N D .2  sm kT q V or C j()V C j()0 1 V  sm kT q A convenient method for determining the barrier voltage ΦSM for a specific metal semiconductor combination is to plot (1/Cj)2 versus voltage. The intercept on the voltage axis is given by ΦSM - KT/q. Note: The capacitance versus voltage relation is governed by the barrier seen in the semiconductor while the current voltage relationship is governed by ΦB, the barrier seen by electrons in the metal. These barriers differ in potential by the separation of the Fermi level in the semiconductor from the conduction band divided by the electronic charge or (eC - ef)/q. 2. Overlay Capacitance As seen in Figure 5, the overlay capacitance C O is the parasitic capacitance of the contact met- allization extending beyond the active junction area and over the passivating oxide. If the effects of surface charges on the semiconductor or depletion of the semiconductor-SiO 2 interface by the applied voltage are neglected, the overlay capacitance can be modeled as a parallel plate capacitor with the SiO2 layer as a dielectric. Then CO becomes: (4) C O . 1 A 1 W O S  = electric permittivity of the semiconductor ND = donor density in n-layer ΦSM = barrier voltage seen by electrons in the semiconductor for traversal into the metal V = applied voltage Cj(0) = junction capacit ance at zero volts where:

Visit www.macomtech.com for additional data sheets and product information. M/A-COM Technology Solutions Inc. and its affiliates reserve the right to make changes to the product(s) or information contained herein without notice. Principles, Applications and Selection of Receiving Diodes Rev. V1 AG314 ADVANCED: Data Sheets contain information regarding a product M/A-COM Technology Solutions is considering for development. Performance is based on target specifications, simulated results, and/or prototype measurements. Commitment to develop is not guaranteed. PRELIMINARY: Data Sheets contain information regarding a product M/A-COM Technology Solutions has under development. Performance is based on engineering tests. Specifications are typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available. Commitment to produce in volume is not guaranteed. where: The overlay capacitance is a parasitic element which should be minimized for optimum diode performance. Reducing C O to a minimum value becomes especially important for frequencies above X band, but there is a trade-off with the contact size. It is normally very difficult to attach wire bonds to contact sizes smaller than 1-2 mils. When junction capacitances for Schottky di- odes are specified they normally include this overlay capacitance. Usually C O is no more than ~0.02 pF for 1-2 mil diameter contact sizes. D. SERIES RESISTANCE The total series resistance shown in Figure 5 consists of the resistance of the undepleted epi- taxial layer (R S1) plus the resistance of the substrate (RS2). A low frequency model, which neglects skin effect, will be discussed. The contribution of the undepleted epitaxial layer to the diode resistance is given by: (5) where: The resistance contributed by the substrate may be modeled by using the resistance of a con- tact dot and the size of the junction on a semi-i nfinite semiconductor substrate. This model is normally valid because the active diode diameter is usually much less than the thickness of the substrate. Using this model, RS2 becomes: 1  = electric permittivity of SiO 2 A1 = area of overlay region (annular ring) W0 = thickness of oxide passivation R S1 A R S1 l ...q  e N D A  = resistivity of undepleted epitaxial layer l = thickness of undepleted epitaxial layer A = area of Schottky junction e  = electron mobility in undepleted epitaxial layer (assumes layer is n-type) ND = donor density in undepleted epitaxial active layer

Visit www.macomtech.com for additional data sheets and product information. M/A-COM Technology Solutions Inc. and its affiliates reserve the right to make changes to the product(s) or information contained herein without notice. Principles, Applications and Selection of Receiving Diodes Rev. V1 AG314 ADVANCED: Data Sheets contain information regarding a product M/A-COM Technology Solutions is considering for development. Performance is based on target specifications, simulated results, and/or prototype measurements. Commitment to develop is not guaranteed. PRELIMINARY: Data Sheets contain information regarding a product M/A-COM Technology Solutions has under development. Performance is based on engineering tests. Specifications are typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available. Commitment to produce in volume is not guaranteed. (6) where: Using equations 5 and 6, the total resistance RS becomes: (7) The above analysis totally neglects skin effect, which may increase the substrate contribution to RS. For a high frequency model, R S1 will be given by the same expression as above, but in or- der to model R S2 one must consider that current will fl ow in a surface layer only one skin depth thick in the substrate. The first component of R S2 to consider will be the spreading resistance of the current into the area directly under the acti ve region one skin depth thick into the substrate. The second will be the resistance of the top surface of the chip. This component may be ap- proximated as the resistance of an annular ring of inner diameter d, outer diameter D, the total chip width, and the thickness d which is the skin depth. The third component of R S is the resistance of the chip side walls, modeled with a thickness d. The total RS at millimeter wave frequencies is the sum of these three components plus the resis- tance of the active epitaxial area. It is normally not necessary to consider skin effects below approximately 50 to 60 GHz for most diodes. E. FIGURE OF MERIT The cutoff frequency (Figure of Merit) of a Schottky barrier diode is maximized by minimizing the RS Cj product. Furthermore, mixer conversion loss (LC) can be shown to be directly proportional to the product of diode series resistance (R S) and junction capacitance (C j). By converting these parameters to semiconductor properties of t he active junction, the following figure of merit for a Schottky barrier diode can be obtained: R S2  S .2d R S2 . S A s  = substrate resistivity d = active junction diameter R S l ..q e N D A . S A

Visit www.macomtech.com for additional data sheets and product information. M/A-COM Technology Solutions Inc. and its affiliates reserve the right to make changes to the product(s) or information contained herein without notice. Principles, Applications and Selection of Receiving Diodes Rev. V1 AG314 ADVANCED: Data Sheets contain information regarding a product M/A-COM Technology Solutions is considering for development. Performance is based on target specifications, simulated results, and/or prototype measurements. Commitment to develop is not guaranteed. PRELIMINARY: Data Sheets contain information regarding a product M/A-COM Technology Solutions has under development. Performance is based on engineering tests. Specifications are typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available. Commitment to produce in volume is not guaranteed. (8) where:  = electric permittivity of the semiconductor W = undepleted epitaxial layer thickness ND = carrier concentration in active region  = carrier mobility in active region .W  . ND

Visit www.macomtech.com for additional data sheets and product information. changes to the product(s) or information contained herein without notice. and/or prototype measurements. Commitment to develop is not guaranteed. typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available. Commitment to produce in volume is not guaranteed. most applications this signal is the difference of the RF and local oscillator frequencies. Figure 7. Frequency Relationships in a Mixer Signals at two different frequencies can produce an output signal at the IF. frequency is either fLO + fIF or fLO - fIF. fIM = fLO - fIF and vice versa.

Visit www.macomtech.com for additional data sheets and product information. changes to the product(s) or information contained herein without notice. and/or prototype measurements. Commitment to develop is not guaranteed. typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available. Commitment to produce in volume is not guaranteed. but at microwave frequencies its shunting action will reduce the RF voltage across the barrier. when packaged diodes are used. Figure 9. Equivalent Circui t of Packaged Mixer Diode

Visit www.macomtech.com for additional data sheets and product information. M/A-COM Technology Solutions Inc. and its affiliates reserve the right to make changes to the product(s) or information contained herein without notice. Principles, Applications and Selection of Receiving Diodes Rev. V1 AG314 ADVANCED: Data Sheets contain information regarding a product M/A-COM Technology Solutions is considering for development. Performance is based on target specifications, simulated results, and/or prototype measurements. Commitment to develop is not guaranteed. PRELIMINARY: Data Sheets contain information regarding a product M/A-COM Technology Solutions has under development. Performance is based on engineering tests. Specifications are typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available. Commitment to produce in volume is not guaranteed. B. BASIC MIXER DIODE RF PARAMETERS A fundamental limitation on the sensitivity of a microwave receiver employing a diode mixer arises from the fact that in the frequency conversion process only a fraction of the available RF signal power is con-verted into power at the intermediate frequency. Some RF signal is also converted to the usually unwanted image frequency and other harmonics, too. This overall loss is dependent primarily on the diode junction properties, and secondarily on the diode's package parasitics (i.e., mismatch of signal power by R S, Cj) and on the match at the input and output ports of the mixer. An additional limitation on performance arises from the fact that the mixer diode itself generates noise (noise temperature ratio) when it is driven by the local oscillator. The conversion loss and the noise temperature ratio are the parameters of most interest in the microwave mixer diode. The mixer diode is completely characterized by the following parame- ters: conversion loss, noise temperature ratio, receiver noise figure, RF impedance and IF impedance. 1) Conversion Loss Theory The conversion loss of a mixer diode is dependent on several factors, including both the package and the Schottky diode die. Conversion loss, LC, can be considered to be the sum of several losses. The first component of total diode conversion loss can be called the matching loss which is de- pendent on the degree of impedance match obtained at both the RF signal and IF ports. Less than optimum match at either of these ports will result in a reduction in the available RF signal at the diode and the inefficient transfer of the IF signal. The matching loss can be expressed as: (9) where SRF, and SIF are RF and IF SWRs respectively. The second component is the loss of signal power due to the diode's parasitic elements and, is called the diode's parasitic loss. The parasitic elements causing this loss are the junction ca- pacitance (C j) and the series resistance (R S). The diode parasitic loss is the ratio of the input RF signal power to the power delivered to the junction variable resistance, Rj: (10) L 1()dB .10 log S RF 1 2 .4S RF log S IF 1 2 .4S IF L 2()dB .10 log P in P out

Visit www.macomtech.com for additional data sheets and product information. M/A-COM Technology Solutions Inc. and its affiliates reserve the right to make changes to the product(s) or information contained herein without notice. Principles, Applications and Selection of Receiving Diodes Rev. V1 AG314 ADVANCED: Data Sheets contain information regarding a product M/A-COM Technology Solutions is considering for development. Performance is based on target specifications, simulated results, and/or prototype measurements. Commitment to develop is not guaranteed. PRELIMINARY: Data Sheets contain information regarding a product M/A-COM Technology Solutions has under development. Performance is based on engineering tests. Specifications are typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available. Commitment to produce in volume is not guaranteed. Expressing this loss in terms of diode parameters: (11) where Rj is the time average value of junction resistance as established by the local oscillator drive level. The minimum value of L2 occurs when Rj is equal to 1/( C j): (12) Since the value of Rj is strongly dependent on the local osci llator drive level, the value of L 2 is a function of LO drive. RS is also a weak function of drive level. If the LO drive is increased above the optimum value, L 2 will increase due to power dissipation in R S, while decreasing LO drive also gives insertion loss increase due to the s hunting effect of the junction capacitance. In gen- eral, for many mixers L2min occurs when Rj is in the range of 250 ohms. This normally occurs at a diode rectified current of approximately 1 to 1.5 mA. The third component is the actual conversion loss at the diode junction. This loss depends mainly on the voltage versus current characteristics of the diode and the circuit conditions at the RF and IF ports. The nonlinear behavior of the diode is represented by a timevarying conduc- tance, G, which is dependent on the DC characteristics of the diode and local oscillator voltage waveform across the diode. Conversion loss and impedance values can then be calculated for the various image terminations by means of linear network theory. The minimum conversion loss (L 3) at the diode junction for a broadband mixer (image properly terminated) in terms of incremental conductances is given by: (13) where g0, g1 and g2 are incremental conductances, which are derived from a series expansion of the diode conductance obtained from the diode I/V equation: L 2()dB .10 log 1 R S R j ... C j

2 R S R j

L 2min()dB .10 log 1 ...2  C j R S L 3min .2 1 1 ..2 g 1 g 0 g 0 g 2 1 1 ..2 g 1 g 0 g 0 g 2

Visit www.macomtech.com for additional data sheets and product information. M/A-COM Technology Solutions Inc. and its affiliates reserve the right to make changes to the product(s) or information contained herein without notice. Principles, Applications and Selection of Receiving Diodes Rev. V1 AG314 ADVANCED: Data Sheets contain information regarding a product M/A-COM Technology Solutions is considering for development. Performance is based on target specifications, simulated results, and/or prototype measurements. Commitment to develop is not guaranteed. PRELIMINARY: Data Sheets contain information regarding a product M/A-COM Technology Solutions has under development. Performance is based on engineering tests. Specifications are typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available. Commitment to produce in volume is not guaranteed. (14) It can be shown that L 3 min approaches, as a limit, a value of ~3 dB. Thus, for an ideal mixer di- ode, the theoretical minimum conversion loss is 3 dB under broadband conditions because a maximum of half the incident RF power is delivered to the IF port and the remaining RF power is dissipated at the image termination. Under narrow band conditions, the image frequency can be reactively terminated such that RF power at the image frequency recombines with the local oscillator signal to improve the conver- sion loss of the diode. Under ideal conditions, t heory predicts that a conversion loss of 0 dB for open or short circuited image terminations can be obtained. Values as low as 1 to 1.5 dB have been obtained in laboratory image recovery mixers. The overall conversion loss, L C, of a mixer diode is the sum of the three loss components, L 1, L2 and L3. (15) or LC = L1 + L2 + L3 (dB) For most production mixers a conversion loss of 4.5 to 6 dB is a reasonable value that can be ob- tained without extensive fine tuning. C. NOISE IN MIXER DIODES 1) Noise Temperature Ratio In variable resistors or varactor mixers, there are three main sources of increased noise. The first is the thermal noise, which is present in all conductors at thermodynamic equilibrium. The second is shot noise, which is generated by moving charge carriers under the influence of an electric field. The third component, which increases with decreasing frequency, is usually referred to as 1/f or flicker noise. The noise temperature ratio includes the effects of all three of these contributors. II S e qV nkT 1 Conversion Loss Matching Loss Parasitic Loss Junction Loss + +

Visit www.macomtech.com for additional data sheets and product information. M/A-COM Technology Solutions Inc. and its affiliates reserve the right to make changes to the product(s) or information contained herein without notice. Principles, Applications and Selection of Receiving Diodes Rev. V1 AG314 ADVANCED: Data Sheets contain information regarding a product M/A-COM Technology Solutions is considering for development. Performance is based on target specifications, simulated results, and/or prototype measurements. Commitment to develop is not guaranteed. PRELIMINARY: Data Sheets contain information regarding a product M/A-COM Technology Solutions has under development. Performance is based on engineering tests. Specifications are typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available. Commitment to produce in volume is not guaranteed. 1C) Thermal Noise The thermal noise for a Schottky barrier is given by the expression: (16) where: 2C) Shot Noise The sources of shot noise in a Schottky barrier are similar to that of pn junctions. In a Schottky diode under forward bias there is a net flow of electrons from the semiconductor to the metal, giving rise to DC current, I. Equal and opposite components of saturation current, I S, also flow across the barrier. These currents do not produce a net current in the external circuit, but do produce shot noise. Total shot noise is attributed to the three components. The resulting shot noise current is given by: (17) In terms of diode AC conductance (G), the noise temperature ratio (t B) of the barrier is defined as: (18) As shown, t B is the ratio of the diode mean square noise current to the mean square thermal noise current of a passive conductance. Using the I/V equation for a Schottky barrier diode, t B can be reduced to (19) The noise temperature ratio, t, of the composite diode, consisting of the Schottky barrier with noise temperature, tB, and series resistance, RS, with its thermal noise is given by the expression i2 ....4 k T G B BIIqi Sn )2(22  kTGB it n B t B .1 2 1 I S II S k = Boltzmann's constant G = diode conductance B = bandwidth under consideration i2 = mean square noise current

Visit www.macomtech.com for additional data sheets and product information. M/A-COM Technology Solutions Inc. and its affiliates reserve the right to make changes to the product(s) or information contained herein without notice. Principles, Applications and Selection of Receiving Diodes Rev. V1 AG314 ADVANCED: Data Sheets contain information regarding a product M/A-COM Technology Solutions is considering for development. Performance is based on target specifications, simulated results, and/or prototype measurements. Commitment to develop is not guaranteed. PRELIMINARY: Data Sheets contain information regarding a product M/A-COM Technology Solutions has under development. Performance is based on engineering tests. Specifications are typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available. Commitment to produce in volume is not guaranteed. (20) where Rj is the dynamic resistance of the barrier (reciprocal of G). Values of t and t B less than one have been measured experimentally for Schottky barrier diodes. When the silicon Schottky barrier diode noise is due entirely to shot noise: (21) The saturation current is usually much smaller than 1. The saturation current, Is, for a platinum- silicon (n-type) Schottky barrier diode is ~2 x 10 -14 amps and the rectified current, I, is usually 0.1 to 1 mA under local oscillator bias conditions. Thus, for ordinary DC forward biases (22) tB 1/2 Under optimum local oscillator excitation, symmetry effects reduce the shot noise to much smaller values. At the same ti me, however, conversion of the source and image thermal noise, together with the series resistance's thermal noise, results in a noise temperature, t, close to 1.0. Normally, Schottky diodes have t < 1.0. 3C) Flicker Noise (1/f) Flicker noise is a type of noise whose magnitude is inversely proportional to the frequency at which it is measured. It occurs in thin metal films, carbon resistors, copper oxide rectifiers, crys- tal varistors and all other semiconductor devices. The causes of flicker noise are not fully un- derstood, although it is probably a surface effe ct due to large dependence of the noise magni- tude upon the condition of the conducting material’s surface and the environment surrounding it. Schottky diodes generally have lower "1/f" noise when compared to point contact diodes and are very suitable for applications involving a low IF frequency, e.g., Doppler radars. In general the lowest 1/f noise is obtained with back dio des. Unpassivated Schottky diodes tend to have less 1/f noise than those with an oxide passivation. However, unpassivated diodes are more susceptible to environmental stresses. D. OVERALL RECEIVER'S NOISE FIGURE The most important criterion of mixer performance is its contribution to the overall receiver's noise figure. The noise at the output of a receiver is the sum of the noise arising from the input jS SBj RR RtRt   * t B .1 2 1 I S II S

Visit www.macomtech.com for additional data sheets and product information. M/A-COM Technology Solutions Inc. and its affiliates reserve the right to make changes to the product(s) or information contained herein without notice. Principles, Applications and Selection of Receiving Diodes Rev. V1 AG314 ADVANCED: Data Sheets contain information regarding a product M/A-COM Technology Solutions is considering for development. Performance is based on target specifications, simulated results, and/or prototype measurements. Commitment to develop is not guaranteed. PRELIMINARY: Data Sheets contain information regarding a product M/A-COM Technology Solutions has under development. Performance is based on engineering tests. Specifications are typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available. Commitment to produce in volume is not guaranteed. termination (source) and the noise contributed by t he receiver itself (i.e., due to the IF amplifier and mixer diodes). The noise factor is the ratio of the actual output noise power of a device to the noise power which would be available if t he device were perfect and merely amplified the thermal noise of the input termination without cont ributing any noise of its own. Noise factor is given by the relation: (23) where: The noise figure is the noise factor in decibels (i.e.): (24) The overall noise figure of a receiver depends on the conversion loss (LC) of the mixer, the noise temperature ratio (t) of the mixer diode and on the noise figure of the IF amplifier (F IF). It is given by the relation: (25) NF = L(t + FIF-1) F S i N i S O N O Si = available signal power at the input of receiver Ni = available noise power at the input of receiver S0 = available signal power at the output of receiver N0 = available noise power at the output of receiver NF( )dB .10 log S i N i S O N O

Visit www.macomtech.com for additional data sheets and product information. M/A-COM Technology Solutions Inc. and its affiliates reserve the right to make changes to the product(s) or information contained herein without notice. Principles, Applications and Selection of Receiving Diodes Rev. V1 AG314 ADVANCED: Data Sheets contain information regarding a product M/A-COM Technology Solutions is considering for development. Performance is based on target specifications, simulated results, and/or prototype measurements. Commitment to develop is not guaranteed. PRELIMINARY: Data Sheets contain information regarding a product M/A-COM Technology Solutions has under development. Performance is based on engineering tests. Specifications are typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available. Commitment to produce in volume is not guaranteed. Mixer diodes are usually specified using F IF of 1.5 dB. This allows comparison of different di- odes under similar test conditions. The mixer noise can also be expressed in terms of mixer input noise temperature, TM: (26) TM = To * to where: E. MIXER DIODE RF IMPEDANCE To = measurement temperature to = Noise temperature of the diode The RF impedance of the variable resistance mixer diode is a property of prime importance in the design of mixers. Any impedance mismatch at the signal and LO frequencies not only results in signal loss due to reflection but also affects the IF impedance at the IF terminals of the mixer. This effect be- comes more serious for mixer diodes with low conversion loss. The RF impedance of a mixer diode can be measured by a SWR method or directly with a network analyzer. The RF imped- ance is affected by local oscillator power. Normally this power is part of its specification. The RF impedance is a complicated function depending on package geometry, size and shape of package parts and composition of the semic onductor and its junction parameters. To estab- lish a good match between a semiconductor chip and RF transmission line, an impedance matching transformer is generally required. F. MIXER DIODE IF IMPEDANCE The IF impedance is the impedance seen looking into the IF port of a mixer. It is important to match this impedance to the IF amplifier input impedance. The pertinent mixer diode IF imped- ance (Z IF) is that impedance at the output terminals of the mixer when the mixer diode is driven by a local oscillator. The IF impedance is a function of the local oscillator power level and also depends on the RF properties of the mixer and circuits connected to the RF terminals of the mixer. The IF impedance of a mixer diode driven by a LO is given in terms of its incremental conductances. For the broadband case it is: (27) Z IF .1 g O 1 ..2 g 1 g O g O g

Visit www.macomtech.com for additional data sheets and product information. M/A-COM Technology Solutions Inc. and its affiliates reserve the right to make changes to the product(s) or information contained herein without notice. Principles, Applications and Selection of Receiving Diodes Rev. V1 AG314 ADVANCED: Data Sheets contain information regarding a product M/A-COM Technology Solutions is considering for development. Performance is based on target specifications, simulated results, and/or prototype measurements. Commitment to develop is not guaranteed. PRELIMINARY: Data Sheets contain information regarding a product M/A-COM Technology Solutions has under development. Performance is based on engineering tests. Specifications are typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available. Commitment to produce in volume is not guaranteed. where gO, g, and g1 are incremental conductances. An accurate measurement of Z IF is essential for measuring noise temperature ratio (t) and con- version loss (L C) of a mixer diode. It is normally done with an admittance bridge. Almost all mixer diodes have their ZIF specified at a moderate RF frequency, i.e. 30-50 MHz, and at a fixed LO drive power level.

Visit www.macomtech.com for additional data sheets and product information. changes to the product(s) or information contained herein without notice. and/or prototype measurements. Commitment to develop is not guaranteed. typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available. Commitment to produce in volume is not guaranteed. Figure 16. Ideal Detector Diode I/V Characteristic

Visit www.macomtech.com for additional data sheets and product information. M/A-COM Technology Solutions Inc. and its affiliates reserve the right to make changes to the product(s) or information contained herein without notice. Principles, Applications and Selection of Receiving Diodes Rev. V1 AG314 ADVANCED: Data Sheets contain information regarding a product M/A-COM Technology Solutions is considering for development. Performance is based on target specifications, simulated results, and/or prototype measurements. Commitment to develop is not guaranteed. PRELIMINARY: Data Sheets contain information regarding a product M/A-COM Technology Solutions has under development. Performance is based on engineering tests. Specifications are typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available. Commitment to produce in volume is not guaranteed. Next, assume that the input signal is amplitude modulated: (31) ∂v = VRF(1 + m sin(wMt) cos(wRFt)) where: Substitution into the Taylor series yields: (32) We are interested in the demodulated components of the above current since the RF currents are bypassed by C1. Therefore, (33) This result shows that I m is proportional to the modulation signal, m sin Mt. It also shows that the video output is proportional to RF power, V RF 2. This is why it is called a square law detector. Finally, note that the conversion efficiency is related to the second derivative of the I/V curve, i.e. the change in slope. (34) V BIAS since . Since ∂2I/∂V2 increases with forward bias, it is evident that the output current at the modulation frequency can be increased by the application of forward bias. The magnitude of the demodulated current: (35) wRF = RF frequency wM = modulation frequency ...)(cos))sin(1(2 1)cos())sin(1( 222 IttmVGIi RFmRF V RFmRFRFBIAS BIAS   t)sin(wmVv I 1t))cos(2w4 mt)(msin(wvv I 1I m RF V m m RF V m BIASBIAS   V I )(2)(2 nkT Iq nkT IIq BIASSBIAS  SBIAS II  nkT qmPGnkT qmV nkT IqmVI RF RF RFBIASRF m  2))((2

Visit www.macomtech.com for additional data sheets and product information. changes to the product(s) or information contained herein without notice. and/or prototype measurements. Commitment to develop is not guaranteed. typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available. Commitment to produce in volume is not guaranteed. Figure 17. Detector Diode Equivalent Circuit common for RRF>Z0, so Ls and Cj serve as a step down transformer.

Visit www.macomtech.com for additional data sheets and product information. M/A-COM Technology Solutions Inc. and its affiliates reserve the right to make changes to the product(s) or information contained herein without notice. Principles, Applications and Selection of Receiving Diodes Rev. V1 AG314 ADVANCED: Data Sheets contain information regarding a product M/A-COM Technology Solutions is considering for development. Performance is based on target specifications, simulated results, and/or prototype measurements. Commitment to develop is not guaranteed. PRELIMINARY: Data Sheets contain information regarding a product M/A-COM Technology Solutions has under development. Performance is based on engineering tests. Specifications are typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available. Commitment to produce in volume is not guaranteed. or The conversion efficiency is P M/PRF = K PRF where K is a constant whose value is determined by the detector diode and detector circuit design. This relation states that conversion efficiency decreases as PRF decreases. This is a fundamental limitation of video detection. RFVM PTkn mqRP  Small signal detection is also limited by noise. In the video detector, 1/f noise dominates. The detection capability of a video detector is characte rized by its tangential signal sensitivity (TSS) which is expressed in dBm. Its relation to video bandwidth is: (39) where B is video bandwidth. A useful relationship is: (40) The sensitivity of a low level video detector depends primarily on the following three factors: the RF matching structure determines the amount of total incident energy that is imposed on the active junction for rectification the rectification efficiency, output impedance and noise properties of the diode determine the response of the diode junction to incident microwave radiation and the input impedance, bandwidth and noise properties of the video amplifier at the detector out- put will affect the overall detector sensitivity. C. DETECTOR DIODE ELECTRICAL CHARACTERISTICS The following section discusses the most importa nt parameters for detector diodes as they are normally used in diode specifications. BTSS  1log1021 BW BWTSSTSS BWBW 

Visit www.macomtech.com for additional data sheets and product information. M/A-COM Technology Solutions Inc. and its affiliates reserve the right to make changes to the product(s) or information contained herein without notice. Principles, Applications and Selection of Receiving Diodes Rev. V1 AG314 ADVANCED: Data Sheets contain information regarding a product M/A-COM Technology Solutions is considering for development. Performance is based on target specifications, simulated results, and/or prototype measurements. Commitment to develop is not guaranteed. PRELIMINARY: Data Sheets contain information regarding a product M/A-COM Technology Solutions has under development. Performance is based on engineering tests. Specifications are typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available. Commitment to produce in volume is not guaranteed. 1) Video Resistance (Rv) Rv is the real part of the diode's small signal impedance. This parameter has been shown to be dependent on the DC bias current and the diode's series resistance. RV = Rj + RS where: Rj can be determined by taking the first derivative of the diode I/V relationship. Rj = small signal junction resistance RS = diode series resistance (41) (42) or where: Normally IS << I, then (43) or for the case of n = 1, T = 300 K, and I is ex pressed in mA. Most common video detectors will have video impedances in the range of 500 to 10K ohms in normal usage. II S e qV nkT 1 1)(  dV dIR j R j .nkT q II S IS = saturation current q = electronic charge n = ideality factor T = Temperature (K) R j nkT .qI R j 0.026 I

Visit www.macomtech.com for additional data sheets and product information. M/A-COM Technology Solutions Inc. and its affiliates reserve the right to make changes to the product(s) or information contained herein without notice. Principles, Applications and Selection of Receiving Diodes Rev. V1 AG314 ADVANCED: Data Sheets contain information regarding a product M/A-COM Technology Solutions is considering for development. Performance is based on target specifications, simulated results, and/or prototype measurements. Commitment to develop is not guaranteed. PRELIMINARY: Data Sheets contain information regarding a product M/A-COM Technology Solutions has under development. Performance is based on engineering tests. Specifications are typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available. Commitment to produce in volume is not guaranteed. 3) Current Sensitivity (b) The current sensitivity, b, for a detector diode is the ratio of short circuit video current to the RF input power. (45) where: Iscv = short circuit video current The units of b are milliamps per milliwatt. g and b are related as follows: (46) In terms of diode parameters and physical constants, b can be expressed as: (47) I SVC P IN  . R V where: D. NOMINAL DETECTABLE SIGNAL (NDS) The nominal detectable signal (NDS) is the RF power level that must be applied to the detector diode so that the video power out of the detector is 3 dB higher than the video output noise level. NDS is a measure of the maximum useable sensitivity of a video detector.  .q ...2nkT R S R j ...2 C j q = electronic charge n = ideality factor k = Boltzman’s constant T = absolute temperature Cj = junction capacitance RS = series resistance Rj = junction resistance

Visit www.macomtech.com for additional data sheets and product information. changes to the product(s) or information contained herein without notice. and/or prototype measurements. Commitment to develop is not guaranteed. typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available. Commitment to produce in volume is not guaranteed. a representation of the TSS level measurement. Figure 19. Representation of TSS Measurement TSS signal level to be when the video output signal is 8 dB greater than the video noise signal. therefore is of limited value for describing Schottky barrier detectors.

Visit www.macomtech.com for additional data sheets and product information. M/A-COM Technology Solutions Inc. and its affiliates reserve the right to make changes to the product(s) or information contained herein without notice. Principles, Applications and Selection of Receiving Diodes Rev. V1 AG314 ADVANCED: Data Sheets contain information regarding a product M/A-COM Technology Solutions is considering for development. Performance is based on target specifications, simulated results, and/or prototype measurements. Commitment to develop is not guaranteed. PRELIMINARY: Data Sheets contain information regarding a product M/A-COM Technology Solutions has under development. Performance is based on engineering tests. Specifications are typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available. Commitment to produce in volume is not guaranteed. G. VIDEO BANDWIDTH Although the detector diode itself may have a wide bandwidth capability, the circuit in which the detector diode is used will determine the video bandw idth of the overall detector. The typical detector circuit, shown in Figure 15, has its low frequency video response limited by the Induc- tance of the RF choke and the series coupling capacitor to the video amplifier. The high frequency video response is limited by the amplifier input impedance and the RF bypass capacitance. The upper frequency 3 dB roll off point is given by: (50) where: f 3dB R V R A ....2  R V R A C T RV = detector diode video resistance RA = amplifier input resistance CT = sum of amplifier input capacitance and capacitance of RF bypass capacitor IV. Comparison Of Mixers And Detectors For Receiving Systems A. CHOICE OF MIXERS VS. DETECTORS Mixers and detectors both downconvert microwave signals so that they may be displayed or processed further. Low noise amplification (up to 100 dB) is more readily achieved at VHF and below than at microwave frequencies. Most mixer (superheterodyne) systems use IF amplification at an intermediate frequency (30 - 200 MHz) and then use a second down converter such as a video detector to recover the modulating signal that was superimposed on th e microwave carrier. Such a superheterodyne detection system is shown in Figure 21. A microwav e receiver with 10 dB noise figure and 1 MHz IF bandwidth would have a maximum sensitivity of - 104 dBm. A single detection system is shown in Figure 22. Such a system, using only video amplifi- cation, can achieve a tangential signal sensitivity (TSS) of perhaps - 60 dBm for a 1 MHz video bandwidth compared with the - 104 dBm for the super heterodyne system. However, the single detection system has the advantage of simplicity, low cost and potentially wide bandwidth.

Visit www.macomtech.com for additional data sheets and product information. changes to the product(s) or information contained herein without notice. and/or prototype measurements. Commitment to develop is not guaranteed. typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available. Commitment to produce in volume is not guaranteed. the signal port is determined by the directivity of the coupler and the diode's impedance match. cations since the LO can be radiated by the receiver antenna. be present and must also be suppressed by filtering, as required by the receiver system design. noise signals are present at the signal and image frequencies. Figure 23. Single Ended Mixer Schematic

Visit www.macomtech.com for additional data sheets and product information. changes to the product(s) or information contained herein without notice. and/or prototype measurements. Commitment to develop is not guaranteed. typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available. Commitment to produce in volume is not guaranteed. separation of the LO and RF inputs. Figure 24. Balanced Mixer

Visit www.macomtech.com for additional data sheets and product information. changes to the product(s) or information contained herein without notice. and/or prototype measurements. Commitment to develop is not guaranteed. typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available. Commitment to produce in volume is not guaranteed. Figure 25. 180° Balanced Mixer Utilizing a Magic Tee as the Bal- order to obtain optimum conversion loss.

Visit www.macomtech.com for additional data sheets and product information. changes to the product(s) or information contained herein without notice. and/or prototype measurements. Commitment to develop is not guaranteed. typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available. Commitment to produce in volume is not guaranteed. Figure 26. 90° Hybrid Mixer for optimum conversion loss. or microstrip transmission media. coupled arms at the expense of SWR and vice versa for the 90° hybrid mixer. normally specified at approximately 1 mA rectified current.

Visit www.macomtech.com for additional data sheets and product information. changes to the product(s) or information contained herein without notice. and/or prototype measurements. Commitment to develop is not guaranteed. typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available. Commitment to produce in volume is not guaranteed. as the circuit are well balanced. Figure 27. Double Balanced Mixer

Visit www.macomtech.com for additional data sheets and product information. M/A-COM Technology Solutions Inc. and its affiliates reserve the right to make changes to the product(s) or information contained herein without notice. Principles, Applications and Selection of Receiving Diodes Rev. V1 AG314 ADVANCED: Data Sheets contain information regarding a product M/A-COM Technology Solutions is considering for development. Performance is based on target specifications, simulated results, and/or prototype measurements. Commitment to develop is not guaranteed. PRELIMINARY: Data Sheets contain information regarding a product M/A-COM Technology Solutions has under development. Performance is based on engineering tests. Specifications are typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available. Commitment to produce in volume is not guaranteed. power level of the two tone intermodulation products because less RF voltage appears across each diode for a given RF input power level. 1) Distortion Products There are several forms of distortion products which occur in all types of mixers. With a single frequency input to the mixer, single tone distortion or harmonic intermodulation distortion pro- duces signals which distort the desired IF outpu t. For systems with a narrow band IF the single tone distortion products will occur primarily out of the IF band. However, for wide band IF mix- ers, some of these intermodulation products can be troublesome. As the power of the single RF input increases, conversion loss compression may occur. This produces a second form of dis- tortion. If the power level of the RF signal to the mixer is kept well below the power level of the LO, (i.e. ~15 dB down) the mixer’s RF-to-IF conversion loss is constant and independent of the RF signal drive power. However, as the RF signal power increases and approaches the same power level as the LO, conversion loss compression occurs, because the RF signal will also for- ward bias the diodes in the ring. This distorts the normal phase relationships of the mixer which were established by the LO signal. This distortion occurs when the RF voltage is large enough to bias the nonconducting diodes into conduction or the conducting diodes into nonconduction. Increasing the LO drive power incrementally does not significantly improve the conversion loss 1 dB compression point since a great deal more LO power is required to sufficiently increase the reverse bias voltage across the nonconductin g diodes. Use of a dual ring quad which uses two diodes connected in series in each leg of the ring increases the mixer's conversion loss compression level because the effective barrier voltage of each leg of the ring quad has been doubled. Each leg’s apparent reverse breakdown voltage is also increased to the sum of the individual diode’s breakdown voltages. However, this type of double balanced mixer will usually have a higher conversion loss due to the increase in series resistance of each leg of the quad. When two RF input signals are present simultaneously, two tone intermodulation occurs. This form of distortion is particularly troublesome because some of the intermodulation products are within the desired IF bandwidth. These distortion components are not easily removed by symmetry or filtering. The double balanced mixer will provide cancellation of AM noise from the local oscillator and LO-to-RF isolation equal to that of a single balanced mixer without the bandwidth restrictions imposed by the 3 dB coupler. Higher dynamic range is also obtained with a double balanced mixer due to the higher levels of LO power which can be used with four diodes. Lower IF im- pedance which is the result of four diodes in parallel is another benefit. However, impedance matching of the RF and LO ports is more difficult because each port sees the impedance of two diodes in series. This impedance can be quite high.

Visit www.macomtech.com for additional data sheets and product information. changes to the product(s) or information contained herein without notice. and/or prototype measurements. Commitment to develop is not guaranteed. typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available. Commitment to produce in volume is not guaranteed. Figure 28. Double-Double Balanced Mixer

Visit www.macomtech.com for additional data sheets and product information. changes to the product(s) or information contained herein without notice. and/or prototype measurements. Commitment to develop is not guaranteed. typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available. Commitment to produce in volume is not guaranteed.

1. the signal frequency (f RF)
2. the desired lower frequency (f
3. and the LO frequency plus IF (f LO-fIF), which is called the image frequency, fIM (see Figure

Figure 29. Frequency Components of a Mixer can be rejected by phasing techniques.

Visit www.macomtech.com for additional data sheets and product information. changes to the product(s) or information contained herein without notice. and/or prototype measurements. Commitment to develop is not guaranteed. typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available. Commitment to produce in volume is not guaranteed. divider (see Figure 30). The IF outputs of each mixer are then combined through a 90° hybrid. depends on the amplitude and phase balance between the two mixers. because the 3 dB hybrid splits the incoming RF si gnal without much degradation of noise figure. mixer can eliminate image noise amplified by the RF amplifier. Figure 30. Image Reject Mixer double balanced mixer will still apply.

Visit www.macomtech.com for additional data sheets and product information. changes to the product(s) or information contained herein without notice. and/or prototype measurements. Commitment to develop is not guaranteed. typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available. Commitment to produce in volume is not guaranteed. more cost effective (lower frequency) local oscillator design. effective LO power decreases. canceled at all three ports. Only odd LO ± even RF and even LO ± odd RF are generated. Unfortunately the LO, IF and RF ports are not isolated. All have the same frequency outputs. Filters are needed for signal selection and isolation. Figure 31. Unbalanced Subharmonically Pumped Mixer

Visit www.macomtech.com for additional data sheets and product information. changes to the product(s) or information contained herein without notice. and/or prototype measurements. Commitment to develop is not guaranteed. typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available. Commitment to produce in volume is not guaranteed. that of an unbalanced subharmonic mixer. Figure 32. Balanced Subharmonically Pumped Mixer and noise figure are required.

Visit www.macomtech.com for additional data sheets and product information. changes to the product(s) or information contained herein without notice. and/or prototype measurements. Commitment to develop is not guaranteed. typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available. Commitment to produce in volume is not guaranteed. can be made approximately linear with the phase angle for small variations of the angle. Figure 35. Phase Detector Performance Curve Illustrating the

Visit www.macomtech.com for additional data sheets and product information. M/A-COM Technology Solutions Inc. and its affiliates reserve the right to make changes to the product(s) or information contained herein without notice. Principles, Applications and Selection of Receiving Diodes Rev. V1 AG314 ADVANCED: Data Sheets contain information regarding a product M/A-COM Technology Solutions is considering for development. Performance is based on target specifications, simulated results, and/or prototype measurements. Commitment to develop is not guaranteed. PRELIMINARY: Data Sheets contain information regarding a product M/A-COM Technology Solutions has under development. Performance is based on engineering tests. Specifications are typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available. Commitment to produce in volume is not guaranteed. I. OTHER RING QUAD APPLICATIONS Other applications of the double balanced mixe r include attenuators, switches and biphase modulators. When an RF signal is applied to the LO port and no signal applied to the IF port, the RF output is isolated from the LO input by 20 to 30 dB. If a positive DC voltage is applied to the IF port, the RF applied signal will be transmitt ed to the RF port with a specific phase. If a negative voltage is applied at the IF port, the RF input signal will be transmitted to the RF port with the same amplitude but in the opposite phase. It is therefore possible to modulate the RF signal through 180° using alternate polarity DC voltage on the IF port. This modulating tech- nique is very useful for digital communications where the IF signal (modulation) can be a stream of binary data. A double balanced mixer can be used as an attenu ator by varying the level of the DC current applied to the IF port. This can control the level of the LO signal transmitted to the RF port. By changing the current level from 0 to 2 mA per diode a current controlled attenuator can be pro- duced. The maximum attenuation will depend on the mixer's isolation. Values of 20 - 30 dB are normally obtainable. J. BRIDGE QUAD APPLICATIONS 1) Biasable Bridge Quad Mixers Bridge quads can be employed in biasable bridge quad Schottky diode mixers (see Figure 37). A biasable mixer is very attractive in applications where little LO power is available. In a bridge quad, the diodes are arranged in a rectifier ring (see Figure 37). The bridge quad circuit still pro- vides good LO-to-RF isolation because, like the double balanced mixer, the RF and LO signals are applied at each other’s virtual ground points. The bridge quad does not provide RF-to-IF isolation, because the IF must be coupled from the RF signal connection points. An IF filter is necessary to separate the RF and IF. Unlike a ring mixer, the biasable bridge quad mixer does not have the proper symmetry to suppress even harmonics of both the RF and LO. It will have spurious signal levels that are dependent upon which ports are chosen to receive the LO and RF signals. There is less distortion if the IF is taken from the RF signal connection ports. In the normal mode of operation, mixing products having even harmonics of the RF will be suppressed. A biasable bridge quad mixer operates as follows. The LO pumps all four diodes in phase. The RF is short-circuited when the diodes are on (forward biased) and open-circuited when the di- odes are off. In these two states the reflection coefficients are -1 and + 1, respectively. The out- put IF signal for a bridge quad mixer is the produ ct of the RF incident signal and the periodic square wave reflection coefficient. Since the al ternating reflection coefficient is "square like", (i.e. on or off) it produces reflection coefficients in the frequency domain of odd harmonics only as shown in Figure 37.

Visit www.macomtech.com for additional data sheets and product information. changes to the product(s) or information contained herein without notice. and/or prototype measurements. Commitment to develop is not guaranteed. typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available. Commitment to produce in volume is not guaranteed. Figure 38. Bridge Quad Sampling Circuit with a minimum of spurious signals. input signal, but they are in series to the output signal (ee Figures 39a and 39b). ics of the input signal frequency. There is no DC voltage generated across the diode pair.

Visit www.macomtech.com for additional data sheets and product information. changes to the product(s) or information contained herein without notice. and/or prototype measurements. Commitment to develop is not guaranteed. typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available. Commitment to produce in volume is not guaranteed. dependent upon the balance of the diodes in the bridge circuit (see figure 40). Typical doubler conversion losses are in the range of 6 to 10 dB and dependent on drive levels. higher reverse breakdown voltage and lower series resistance than similar silicon diodes. modulators (as described in Section I), a 90° hybrid and an in-phase combiner. DC voltage pulses through the IF port. These pulses are the 0° and 180° modulation inputs. suppressed carrier signal. All even and half of the possible odd harmonics are also suppressed. Figure 41. Quadrature Phase Modulator Block Diagram

Visit www.macomtech.com for additional data sheets and product information. changes to the product(s) or information contained herein without notice. and/or prototype measurements. Commitment to develop is not guaranteed. typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available. Commitment to produce in volume is not guaranteed. or it can determine if the frequency of an RF signal is above or below that of a known LO signal. same frequency. Figure 42 shows the circuit of a typical QIFM. The LO or known frequency is fed through an in-phase power divider to two quadrature mixers. lag the signal from IF port 1. output voltage proportional to the relative phase angle between the signals (see Figure 35). lower in frequency when the target is receding from the radar system. Figure 42. Block Diagram of the Quadrature IF Mixer 5

Visit www.macomtech.com for additional data sheets and product information. M/A-COM Technology Solutions Inc. and its affiliates reserve the right to make changes to the product(s) or information contained herein without notice. Principles, Applications and Selection of Receiving Diodes Rev. V1 AG314 ADVANCED: Data Sheets contain information regarding a product M/A-COM Technology Solutions is considering for development. Performance is based on target specifications, simulated results, and/or prototype measurements. Commitment to develop is not guaranteed. PRELIMINARY: Data Sheets contain information regarding a product M/A-COM Technology Solutions has under development. Performance is based on engineering tests. Specifications are typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available. Commitment to produce in volume is not guaranteed. N. SINGLE SIDEBAND MODULATORS 12 Single sideband (SSB) m odulators are used to modulate a carrier signal with a low frequency baseband signal and transmit only one sideband. Single sideband modulators are often used in digital cellular telephone transmitters. They provide the interface between the digitally encoded voice and the RF transmission channel by converting the I and Q signals from the channel codec into the RF signal that the telephone transmits. Es- sentially, they modulate a high frequency carrier with the lower frequency voice data to create all forms of analog and digital modulation. Where practical, a direct modulation technique is pre- ferred because it eliminates much of the filteri ng and LO requirements necessary for multiple up conversion transmitter topologies. The output signals of the symbol modulator, which are two orthogonal analog signals: an in-phase (I) signal and a quadrature (Q) signal to accommodate phase information, are input to the I and Q ports of the single sideband modulator. The amplitudes of these signals are analogous to the X and Y values in a Cartesian plane. The modulation process is analogous to a rectangular-to-polar coordinate conversion with the vector-summed I and Q transitions producing data-bit-specific RF phase transitions. With proper scaling of the I and Q input ratios, the vector sum of the I and Q channels forms a vector of any phase or amplitude. In cellular radio systems, the ch annel carrier spacing is very nar row compared to the modulating frequency. Therefore, the third harmonic of the modulating frequency must be suppressed to re- duce interchannel interference. Unlike the QPSK modulator (as described in section L), the SSB modulator must handle the data as a linear signal with the RF carrier acting as the higher power level (LO) signal. For example, the DCS1800 and GSM standards use Gaussian minimum-shift- keying (GMSK) modulation. GMSK makes use of band-limited modulating data to minimize the requirement for output filtering at RF. Due to this band-limiting, the RF output is also band-limited when a linear modulator is used. This enables the system to meet stringent channel bandwidth requirements, thereby compressing many RF channels together to maximize user capacity. A SSB modulator can be built as shown in Figure 43. The input carrier signal is applied to an in- phase, 3 dB power divider selected for the frequen cy band of interest. The outputs of this power divider feed two double balanced mixers with DC-coupled IF ports for audio modulation. The modulating signal is applied to the IF ports of the mixers through an IF 90° 3 dB hybrid. The outputs of the two mixers are combined by a 90° 3 dB hybrid covering the carrier signal band.

Visit www.macomtech.com for additional data sheets and product information. changes to the product(s) or information contained herein without notice. and/or prototype measurements. Commitment to develop is not guaranteed. typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available. Commitment to produce in volume is not guaranteed. Figure 43. Block Diagram of the Single Sideband Modulator 5 out of phase and is canceled.  IF1, the upper side band is produced at the RF output.  IF2, the lower side band is produced at the RF output. is not critical and 1 to 1000 MHz hybrids work well.

Visit www.macomtech.com for additional data sheets and product information. changes to the product(s) or information contained herein without notice. and/or prototype measurements. Commitment to develop is not guaranteed. typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available. Commitment to produce in volume is not guaranteed. is used the IF is the baseband modulating signal. Figure 44. Mixer Frequency Relationships

Visit www.macomtech.com for additional data sheets and product information. M/A-COM Technology Solutions Inc. and its affiliates reserve the right to make changes to the product(s) or information contained herein without notice. Principles, Applications and Selection of Receiving Diodes Rev. V1 AG314 ADVANCED: Data Sheets contain information regarding a product M/A-COM Technology Solutions is considering for development. Performance is based on target specifications, simulated results, and/or prototype measurements. Commitment to develop is not guaranteed. PRELIMINARY: Data Sheets contain information regarding a product M/A-COM Technology Solutions has under development. Performance is based on engineering tests. Specifications are typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available. Commitment to produce in volume is not guaranteed. B. TYPES OF MIXERS BY FREQUENCY OUTPUT 1) Down Converter (Mixer) In a down converter (usually simply called a mixer) the desired IF output signal is obtained from the difference of the LO and RF signal frequency. Normally it is at only a small fraction of the signal frequency. 2) Up Converter (Modulator) In an up converter the input signals will be the LO and the IF signals. The RF output signal is the LO + IF. Normally the IF signal is modulated prior to up conversion. C. MIXER DIODE TERMS (CHARACTERISTICS) 1) Conversion Loss Conversion loss is the loss of signal power that results from the conversion from the RF signal frequency to the IF frequency in a down converter or conversion from the IF signal frequency to the RF frequency in an up converter. It is defined as a power ratio: (52a) Conversion loss may also be expressed in dB: (52b) When referred to a mixer diode, it is the loss in an optimum single ended mixer carefully designed to minimize losses in the RF and LO coupling networks. Conversion loss normally includes power transferred to the image frequency which is resistively terminated. 2) Noise Figure The noise factor and noise figure (NF) of a mixer diode are closely related to its conversion loss. Noise factor and noise figure are usually measured single sideband in a single ended mixer. Noise factor is the ratio of the signal to noise ratio at the mixer input to the signal to noise ratio at the mixer output. L C IF Output Power RF Signal Input Power L C 10 log IF Output Power RF Signal Input Power

Visit www.macomtech.com for additional data sheets and product information. M/A-COM Technology Solutions Inc. and its affiliates reserve the right to make changes to the product(s) or information contained herein without notice. Principles, Applications and Selection of Receiving Diodes Rev. V1 AG314 ADVANCED: Data Sheets contain information regarding a product M/A-COM Technology Solutions is considering for development. Performance is based on target specifications, simulated results, and/or prototype measurements. Commitment to develop is not guaranteed. PRELIMINARY: Data Sheets contain information regarding a product M/A-COM Technology Solutions has under development. Performance is based on engineering tests. Specifications are typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available. Commitment to produce in volume is not guaranteed. (53) (54) where: Normally this simplifies to N F ~ 10 log LC (fIF-1) For a perfect mixer diode, NF( in dB) = 3.0 dB plus the IF amplifier noise figure and any circuit losses. 3) SWR or Match SWR or match refer to the input standing wave ratio (SWR) of a single diode in a fixed tuned holder at the LO frequency. This is normally stated at a fixed LO drive, normally enough to produce ~1 mA of rectified current. 4) IF Impedance IF impedance is the average of the time varying impedance of a mixer diode at a nominal IF fre- quency (usually 30 MHz). It is measured with an admittance bridge at a fixed rectified current (normally 1 mA) set up by the LO drive. Most Schottky diodes will have IF impedances in the range of 150-400 ohms at 1 mA. 5) Burn Out Mixer diodes can be destroyed by static discharge or excessive incident RF power. Most Schottky diodes fail by becoming a short circuit. Burn out is defined as the maximum RF power which the diode can withstand without damage. It normally is in the range of 50 to 500 mW CW and up to 1 to 5 watts for pulses less than 2 to 5 nanoseconds long. Noise_factor Signal in Noise in Signal out Noise out NF .10 log L C T M f IF 1 LC = diode conversion loss (expressed as a power ratio) TM = diode effective temperature ratio (normally < 1.0) fIF = IF amplifier noise figure (expressed as a ratio)

Visit www.macomtech.com for additional data sheets and product information. changes to the product(s) or information contained herein without notice. and/or prototype measurements. Commitment to develop is not guaranteed. typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available. Commitment to produce in volume is not guaranteed. perature ratio begins to rise rapidly. It normally increases as the inverse of the IF frequency. single frequency, i.e. 100 Hz or 1 kHz as required by the system. the semiconductor9. Barrier height is expressed in term of volts or electron volts. show the approximate local oscillator power requirement vs. barrier height. nal to noise ratio of 2.5:1 is produced. TSS usually is measured on an oscilloscope (see below). MHz. It is expressed in dBm (i. e., -55 dBm). Figure 45. TSS

Visit www.macomtech.com for additional data sheets and product information. M/A-COM Technology Solutions Inc. and its affiliates reserve the right to make changes to the product(s) or information contained herein without notice. Principles, Applications and Selection of Receiving Diodes Rev. V1 AG314 ADVANCED: Data Sheets contain information regarding a product M/A-COM Technology Solutions is considering for development. Performance is based on target specifications, simulated results, and/or prototype measurements. Commitment to develop is not guaranteed. PRELIMINARY: Data Sheets contain information regarding a product M/A-COM Technology Solutions has under development. Performance is based on engineering tests. Specifications are typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available. Commitment to produce in volume is not guaranteed. 2) Voltage Sensitivity ( γ) Voltage sensitivity ( γ) is a measure of the output voltage available at a standard input power using a defined load resistance (usually 1 megohm). It is normally measured in the square law range of the diode, typically with P IN = -30 dBm. Voltage sensitivity is given in mV/mW. 3) Video Impedance (R V) Video impedance of a detector diode is the Norton equivalent impedance of the diode when it is modeled as an RF-input-voltage-controlled current source. The video impedance of a diode is affected by the DC current flowing in the diode. It is normally specified with a given small DC current, i.e., from 1 to 100 microamperes. Some ZBD (Zero Bias Detector) diodes are us ed without an externally applied bias current. Normal video impedances for these diodes can range from 1-2 kilohms to megohms. The video impedance can affect the pulse fidelity of a video detector as the RC time constant of the ampli- fier/detector depends on RV and the bypass capacitor. The video resistance of a diode is the slope (AC) resistance of a detector diode. It will determine the voltage sensitivity of a detector diode. The video impedance of a diode is the RF impedance looking into the diode from the video amplifier. It is used to match the detector to the video amplifier. E. RECEIVER SYSTEM CHARACTERISTICS 1) Receiver Sensitivity The following equation for the sensitivity of a receiver shows the parameters which affect a receiving system's sensitivity: (55) S = -114 + NFO + 10 logl0 B + 10 log10 (S/N) where: S = receiver sensitivity in dBm B = receiver bandwidth in MHz NFo = receiver overall noise figure in dB S/N = minimum acceptable receiver ou tput signal-to-noise ratio in dB

Visit www.macomtech.com for additional data sheets and product information. M/A-COM Technology Solutions Inc. and its affiliates reserve the right to make changes to the product(s) or information contained herein without notice. Principles, Applications and Selection of Receiving Diodes Rev. V1 AG314 ADVANCED: Data Sheets contain information regarding a product M/A-COM Technology Solutions is considering for development. Performance is based on target specifications, simulated results, and/or prototype measurements. Commitment to develop is not guaranteed. PRELIMINARY: Data Sheets contain information regarding a product M/A-COM Technology Solutions has under development. Performance is based on engineering tests. Specifications are typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available. Commitment to produce in volume is not guaranteed. (56) where: Note: CosΦ = 1 when the target moves directly toward or away from the signal transceiver. Velocity v is expressed as a vector so it determines the sign of the Doppler shift frequency. 3) Typical Doppler Radar System A typical Doppler radar system consists of an RF (i.e., microwave) section, a signal processing section and a bias supply. In order to design a Doppler radar system, one must first know: 1. The maximum range at which the target is to be detected. This determines the overall sensi- tivity required of the transceiver. 2. The maximum and minimum target speeds that the system is to measure. This determines the required frequency characteristics of the IF amplifier. The commercial Doppler systems such as police radars and intrusion alarms usually operate with a "zero IF" because the transmitter source (often a Gunn oscillator) is also used as the lo- cal oscillator for the mixer. Using this technique, the signal amplification is most easily applied to the IF signal at the Doppler shift frequency. For example, if the transmitter frequency is 10.525 GHz, a vehicle traveling 50 mph (80.5 km/hour) will cause a Doppler shift of 1568 Hz. A police radar's IF amplifier bandpass frequency should be approximately 50 Hz to 5000 Hz. f d ...2v f 0 c cos f0 = transmitter frequency in Hz c = velocity of light (3 x 10 8 meters per second) v = velocity of the target (meters per second)  = angle between microwave beam and target's path 2) Doppler Shift Doppler radars utilize the fact that RF energy reflected by a moving target is apparently shifted in frequency as a result of the relative motion between the source and reflecting target. The amount of this frequency shift is directly proportional to the target's velocity relative to the radar's transceiver. The same effect occurs with sound waves when an automobile sounding its horn is moving with respect to an observer. The sound pitch is higher when the horn is moving toward the observer and decreases as it moves away. The Doppler shift frequency f d is given by:

Visit www.macomtech.com for additional data sheets and product information. M/A-COM Technology Solutions Inc. and its affiliates reserve the right to make changes to the product(s) or information contained herein without notice. Principles, Applications and Selection of Receiving Diodes Rev. V1 AG314 ADVANCED: Data Sheets contain information regarding a product M/A-COM Technology Solutions is considering for development. Performance is based on target specifications, simulated results, and/or prototype measurements. Commitment to develop is not guaranteed. PRELIMINARY: Data Sheets contain information regarding a product M/A-COM Technology Solutions has under development. Performance is based on engineering tests. Specifications are typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available. Commitment to produce in volume is not guaranteed. The maximum range of a radar system can be determined by the following equation: (57) R max ..P t G a K F where: This expression shows that the effective range of a radar system is inversely proportional to the fourth root of the overall receiver noise figure. Pt = transmitted power G a = antenna gain expressed as a ratio F = receiver noise figure expressed as a ratio K = a constant

Visit www.macomtech.com for additional data sheets and product information. M/A-COM Technology Solutions Inc. and its affiliates reserve the right to make changes to the product(s) or information contained herein without notice. Principles, Applications and Selection of Receiving Diodes Rev. V1 AG314 ADVANCED: Data Sheets contain information regarding a product M/A-COM Technology Solutions is considering for development. Performance is based on target specifications, simulated results, and/or prototype measurements. Commitment to develop is not guaranteed. PRELIMINARY: Data Sheets contain information regarding a product M/A-COM Technology Solutions has under development. Performance is based on engineering tests. Specifications are typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available. Commitment to produce in volume is not guaranteed. Table I4 Comparison of the Characteristics of Common Mixer Circuits VSWR Port-to-Port Isolation Mixer Type RF LO IF RF/IF LO/RF LO/IF LO Power Requirement P1dB Single Ended Depends on Matching Circuits Depends on Filters Low Low Single Bal- anced (180°) Depends on Matching Circuits Depends on Filters Poor Depends on Filters Moderate Moderate Single Balanced (90°) Good Good Depends on Matching Circuits Depends on Filters Poor Depends on Filters Moderate Moderate Double Balanced Good Good High High Double- Double Balanced Good Good Highest Highest Sub- Harmonic Depends on Matching Circuits Good Depends on Filters Depends on Filters Moderate Low Image Re- ject Good Good Very High High Mixer Type LO AM Noise Rejection LO Spuri- ous Signal Rejection 3rd Order IM Intercept Low order Spurious Response Rejection Single Ended None Depends on Matching Circuits Low None Single Balanced (180°) Good Depends on Matching Circuits Moderate 2fLO ± 2fRF : Good 2fLO ± fRF : Good if Designed to Suppress LO Harmonics fLO ± 2fRF : Good if Designed to Suppress LO Harmonics Single Balanced (90°) Good Good High 2fLO ± 2fRF : Good 2fLO ± fRF : None fLO ± 2fRF : None Double Balanced Good Good High 2fLO ± 2fRF : Good 2fLO ± fRF : Good fLO ± 2fRF : Good Double- Double Balanced Good Good Highest 2fLO ± 2fRF : Good 2fLO ± fRF : Good fLO ± 2fRF : Good Sub- Harmonic Good Depends on Matching Circuits Low Rejects all mixing with odd harmonics Image Reject Good Good High 2fLO ± 2fRF : Good 2fLO ± fRF : Good fLO ± 2fRF : Good

Visit www.macomtech.com for additional data sheets and product information. M/A-COM Technology Solutions Inc. and its affiliates reserve the right to make changes to the product(s) or information contained herein without notice. Principles, Applications and Selection of Receiving Diodes Rev. V1 AG314 ADVANCED: Data Sheets contain information regarding a product M/A-COM Technology Solutions is considering for development. Performance is based on target specifications, simulated results, and/or prototype measurements. Commitment to develop is not guaranteed. PRELIMINARY: Data Sheets contain information regarding a product M/A-COM Technology Solutions has under development. Performance is based on engineering tests. Specifications are typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available. Commitment to produce in volume is not guaranteed. Table II Selection Guide for Diod e Configuration and Material by Type of System Type of Mixer or System Frequency Range Suggested Diode Types Comments Millimeter Receiver Mixers 20 - 100 GHz GaAs Beam Lead GaAs Flip Chip Best noise figure Millimeter Up Converter 20 - 100 GHz GaAs Beam Lead GaAs Flip Chip Lower conversion loss allows higher output power Subharmonic Mixer 20 - 100 GHz GaAs Beam Lead GaAs Flip Chip Better conversion loss, noise figure and dy- namic range High Dynamic Range Mixers

100 MHz - 12 GHz

Highest dynamic range. However, noise figure is a little worse above 10 GHz due to extra Rs of 2nd junction 10 - 20 GHz GaAs Ring Quad Beam Lead or Flip Chip Good IM3, better conversion loss than Si. Larger LO drive than required by Si. Modulator or Sampling Switch

10 MHz - 5 GHz

GaAs can have higher VB than Si but also has higher VF than Si Balanced Mixer 1 - 18 GHz Si - Packaged, Beam Lead or SurMount Si less expensive than GaAs, operates with lower LO power Double Balanced Mixer 1 - 18 GHz Si - Packaged, Beam Lead or SurMount Si less expensive than GaAs, operates with lower LO power Starved LO Mixer 1 - 18 GHz Si - ZBD or Low Barrier Packaged, Beam Lead or SurMount Lowest LO drive requirement Phase Detector or Bi Phase Modulator

100 MHz - 18 GHz

Si - Packaged, Beam Lead or SurMount Match and symmetry of a monolithic quad are better than that of discrete quad Image Reject Mixer 1 - 18 GHz Si Ring Quad - Packaged, Beam Lead or SurMount Match and symmetry of a monolithic quad are better than that of discrete quad

Visit www.macomtech.com for additional data sheets and product information. M/A-COM Technology Solutions Inc. and its affiliates reserve the right to make changes to the product(s) or information contained herein without notice. Principles, Applications and Selection of Receiving Diodes Rev. V1 AG314 ADVANCED: Data Sheets contain information regarding a product M/A-COM Technology Solutions is considering for development. Performance is based on target specifications, simulated results, and/or prototype measurements. Commitment to develop is not guaranteed. PRELIMINARY: Data Sheets contain information regarding a product M/A-COM Technology Solutions has under development. Performance is based on engineering tests. Specifications are typical. Mechanical outline has been fixed. Engineering samples and/or test data may be available. Commitment to produce in volume is not guaranteed. References 1. Dr. A. Carlson, “Principles of Receiving Diodes”, M/A-COM Receiving Diode Handbook, 1980 2. W. Moroney, “Overview of Subharmonic Mixers”, M/A-COM Receiving Diode Handbook, 1980 3. M. Cohen et al, “Harmonic Mixers with Anti Parallel Diode Pairs”, MTT International Sympo- sium, pp. 171 - 172, 1974 4. J. F. Reynolds, Learn the Language of Mixer Specifications”, Microwave Magazine, vol. 17, May, 1978 5. M/A-COM Mixer Products catalog, 1986 1182 - 1196, August, 1970 7. C. F. Genzabella & C. Howell, “Gallium Arsenide Schottky Mixer Diodes”, Symposium on GaAs, 1966 8. S. A. Maas, “Microwave Mixers”, Artech House, 1986 9. S. M. Sze, “Physics of Semiconductor Devices”, 2nd edition, John Miles and Sons, 1981 10. D. Held & A. Held, “Conversion Loss and Noise of Microwave and Millimeter Mixers”, IEEE Transactions, MTT-26, pp. 49 - 61, 1978 11. Y. Anand & C. Howell, “The Real Culprit in Diode Failure”, Microwaves, August, 1970, pp. 1 - 3